1. Field of the Invention
The present invention relates to a current collector for a nonaqueous solvent secondary battery, and to an electrode and a battery, which use the current collector.
2. Description of the Related Art
In recent years, in order to deal with the air pollution and the global warming, reduction of an emission amount of carbon dioxide has been eagerly desired. In the automotive industry, expectations have centered on the reduction of the emission amount of the carbon dioxide, which is brought by introducing an electric vehicle (EV) and a hybrid electric vehicle (HEV), and development of a secondary battery for driving a motor, which holds the key to putting these electric vehicle and hybrid electric vehicle into practical use, has been being actively made.
As such a motor driving secondary battery, a nonaqueous solvent secondary battery such as a lithium ion secondary battery having the highest theoretical energy among all the known batteries has attracted attention, and development of the nonaqueous solvent secondary battery has been advanced rapidly at present.
In general, the lithium ion secondary battery includes a stacked body (battery element) formed by connecting a positive electrode, in which a positive electrode active material and the like are coated on both surfaces of a positive electrode current collector by using a binder, and a negative electrode, in which a negative electrode active material and the like are coated on both surfaces of a negative electrode current collector by using the binder, to each other while interposing an electrolyte layer therebetween. Moreover, for the purpose of extracting electric power to the outside, electrode terminals (positive electrode terminal and negative electrode terminal) are electrically connected to the battery element. Furthermore, in general, the battery element is housed in a metal/resin laminate sheet formed by stacking resin sheets on both surfaces of foil made of lightweight metal such as aluminum so that the electrode terminals can be exposed to the outside (refer to Japanese Patent Application No. 2001-236946).
Here, as the current collectors composing the electrodes of the lithium ion secondary battery, in general, foil made of the metal such as the aluminum is used for the positive electrode, and foil made of metal such as copper is used for the negative electrode.
Then, in the case of manufacturing the electrodes by using these foils as the current collectors, slurries in which the electrode active materials, the binder and the like are dispersed into a solvent are coated on surfaces of the foils, followed by drying, and thereafter, press treatment is implemented therefor by using a method such as roll press. In such a way, active material layers which are flat and have a desired thickness are formed on the surfaces of the foils.